libvpx 1.3

DONE: 
- Building on x86 based processors

TODO:
- Complete ARM source file conversion
- MozCo Bug 938686 - Support Opus in WebM
- MozCo Bug 884275 - Report 'maybe' instead of 'probably' from canPlayType('video/webm')
- MozCo Bug 833023 - Enable VP9 playback in HTML media elements